95 Suburban won't reach 195° with 2 new thermostats

[nh3fix]

Beyond frustrated, I recently installed new intake manifold gaskets, plugs, wires, cap and rotor, thermostat and new coolant. For some reason it will not reach temp. I flushed the system twice and each time installed a new stant SUPERSTAT 195°F test drove it after filling the system 50/50 and thought the problem was cured, it reached 195 and stayed there like it used to. I drove it the next morning and it went to 195 and stayed. GREAT!!! then I left for work and back to the same problem 170°F and not a degree higher. Temps were verified with 2 different meters. The reason I am so concerned is the computer sends more fuel when not at temp and my mileage dropped significantly. Thanks for any suggestions!!

[JWhite8055]

An old trick is to use a piece of cardboard in front of the radaitor to block off some of the airflow to rais engine temps. You'll have to experiment, but once you find the right size piece of cardboard you can then cut a piece of sheet metal and braze it in place.

[lesnola]

I have a 94' 1500 Suburban and what sounds like is happening to you happened to me two years ago. I took my suburan to a dealer in Monroe, La. and they determined that my heater core was stopped up and could not be repaired. So after my wallet was lightened up by $ 200 I was on my way with no more problems.

Hope this helps,


lesnola

[JWhite8055]

I would think that a clogged heater core would raise the temperature rather than lower it.

[lesnola]

On the lowering or raising the coolent temp: The Suburban 1500 heater core runs with constant coolent circulating in it - air conditoner off or on. I am not familiar with where GM runs their coolent lines under the hood. In any case on my 1500, the dealer ran air through the disconnected heater core and still had a dimished air exaust even after running industrial strength radiator clean-out through the system. All I am saying is this may be one item to check out.


Lesnola

[nh3fix]

Thanks for the ideas, I believe the problem is air in the system after talking to several mechanics. I disconnected the heater lines and installed a jumper from the manifold to the pump and was able to get a bunch of air out of the system before connecting the jumper.
Holds temp now but I still have to figure out how to purge the air out of the rear heater core. I capped the lines so they wouldn't drain out for now.

[lesnola]

nh3fix;

It looks like you have found the fix for your Suburban. As far as air in the heater core; when I was stuck at the Chev. dealer , in Monroe La., I watched the process of filling the system with coolent. They simply hooked up the hoses to the new heater core. Next, coolent was added at the radiator cap until full. Engine RPM was raised several time to flush any traped air in the core or system. I think the theory on this is that the outlet side of the heater core heads back to the radiator where air trapped in the core would come up to the top of the radiator top. It sounds like you got good advice from the group of mechanics you talked to. I would run the above advice on the fill up of the coolent, in the heater core, with one of these mechanics, before you go any further.


lesnola